WeatherSolve Structures - Ultra Span Productive Environments for all Weathers

THE VALUE OF THE MATERIAL LOST

For bulk materials such as coal, the value is usually just the delivered cost.
For ores such as copper the calculation must be adjusted to allow for the higher percentage of copper in the fines. In the earth the copper-rich material is deposited in veins in the rocks. The material is weaker than the rock, so when mined it splits at the veins leaving the copper-rich material exposed. Fines can assay out from two to six times richer than the rest of the ore. This makes ore-dust very valuable.

 

HOW MUCH CAN BE RETAINED?
The effectiveness of dust control systems is discussed in other pages on this website such as Dust Control.
The effectiveness is dependent on a number of factors. These factors include the winds, the topography, the design of the windbreak and the use of supplementary loss control devices such as fog or surfactant. The levels and the size ranges of the fines also influence the effectiveness of the control systems.

For most situations, it is practicable to retain 70% to 90% of the material that would otherwise be blown away.

 

CASE STUDY ONE
A coal-fired power plant has an 8 acre storage pile. The pile is fed by a 70ft high conveyor dropping coal about 30ft. They had been measuring their losses for some years and found they averaged out at 3.2% losses annually. Throughput is 2.5 million tons annually.

The solution was a 70ft high windbreak on two sides of the pile at a cost of $600,000. Calculated losses were then 1.1%. Coal is $22 per ton.

 

Annual savings with windbreak:

 

(3.2 - 1.1)% Windbreak cost Repayment period:

$1,155,000 $   600,000 0.5 years

    

CASE STUDY TWO
A copper mine has conveyor-fed stockpiles. The drop is typically 30ft to 60ft.The calculated losses were 1.5% annually The throughput on the conveyors is 50 million tons annually
The mine assay levels were 0.4%, but the fines assayed out at over 1%. Let us (very conservatively) assume that the copper price is $0.75 per pound, but that processing costs are $0.50 per pound. Fines lost from the stockpile are worth their copper content less the cost of processing the ore on the stockpile. That is: 2000 x 1% x $(0.75 - 0.5) = $5.00 per ton.

The solution was a 80ft to 100ft high windbreak alongside the piles. The cost of the windbreak was $2,100,000.The calculated effect of the windbreaks was to cut the losses to 0.5%.

Annual savings with windbreak:

 

(3.2 - 1.1)%   Windbreak cost  Repayment period:

$2,500,000 $2,100,000 0.9 years

                         
                                                      

The case studies show how quickly the cost of a windbreak dust control system can be recovered. The returns are so good that one may be forgiven for wondering why there are not windbreaks around every stockpile.

The answer is that firstly, the vast bulk of the dust is lost to the atmosphere and so is not obvious. “Out of sight out of mind” applies, so with the problem not obvious, the push to implement a solution  reduces. Only when billions of tons of dust are lost to the atmosphere such as occurred in the 1930’s in South Western USA or more recently in China are the effects obvious. 

Secondly, the difficulty in finding a viable solution has affected the level of implementation. When applied to tall industrial windbreaks, traditional windbreak systems were often not suitable as there was no way to put the poles further than about 15ft apart. The Ultra Span technology offered by WeatherSolve Structures Inc. overcomes this problem. The Ultra Span industrial windbreak system enables windbreaks to be built much taller, much more economically, and much more durably than has been the case in years past.

For help getting base data to calculate the economic returns on your own stockpiles, please contact your WeatherSolve authorized agent.